Monday 4 February 2008 21.42 EST
First published on Monday 4 February 2008 21.42 EST

A former detective last night said that he was the officer who had bugged a conversation between a Labour MP and a terrorism suspect held in prison.

Mark Kearney, 49, whose duties included operations at Woodhill prison in Buckinghamshire, said that he had been under "significant pressure from the Metropolitan police" to covertly record a conversation between Sadiq Khan MP and his constituent Babar Ahmad.

Kearney retired from Thames Valley police last year after 30 years of service, having been charged with several counts of misconduct in public office. He told the BBC: "I did record the visit but have never thought it was justified in these circumstances."

He said he was concerned that senior officers in his force were authorising bugging of an MP's conversations.

The justice secretary, Jack Straw, has said that the first he had heard of the matter was at the weekend, despite a Tory claim they brought it to the attention of No 10 in December through a letter from the shadow home secretary, David Davis. Downing Street denied any knowledge of the letter.

But a Ministry of Justice spokeswoman did say last night: "MoJ officials became aware in December of issues concerning visits to Woodhill prison by Sadiq Khan MP." Mr Davis questioned why ministers had not been informed.

Police bugged a conversation between Khan and Ahmad as the pair discussed a civil action the inmate was bringing against the commissioner of the Metropolitan police, Sir Ian Blair, for an alleged assault by Scotland Yard officers, it was claimed yesterday.

At least two conversations between the men were monitored at the request of Scotland Yard's anti-terrorism branch, sources confirmed yesterday.

They claimed that the conversations between Ahmad and those visiting him in jail were bugged between 2004 and 2006, and that the conversations with Khan had not been a specific target of the police.

Last night a Daily Mail report suggested that conversations between Ahmad and Khan had been recorded in 2004, before Khan became MP for Tooting, south London, at the 2005 general election.

With questions mounting about the police's involvement and the use of their powers, Straw yesterday announced an inquiry into the allegations, to be headed by a former judge.

Ahmad's lawyer told the Guardian that during the second bugged conversation in June 2006, Khan discussed with his constituent the civil action for an alleged assault in December 2003 when Ahmad was first arrested.

Ahmad's solicitor, Fiona Murphy, has written to the prison service saying that the conversation had apparently "been covertly recorded in contravention of the Wilson doctrine". Scotland Yard refused to answer questions yesterday.

Two sources say that an operation monitoring Ahmad began after his arrest and imprisonment following the US extradition request in 2004, and ran through to at least summer 2006.

However, senior Met officers are particularly worried about the accusation that they singled out Khan, a former rights lawyer who represented clients who had successfully sued the police.

Before the visits in May 2005 and June 2006 Khan would have submitted a visiting order. Sources say it was not clearly stated that Khan was an MP - and thus officers involved may not have realised a doctrine banning the bugging of MPs should have applied.

The bugging, using a device secreted under a table over which the two men talked, was by Thames Valley police but was requested by Scotland Yard's anti-terrorism branch, which in Deceber 2003 originally made the arrest Ahmad was suing over; he was released after six days without charge.

He then made an official complaint about the alleged assault, claiming he was kicked and punched, and taunted by an officer who said: "Where is your God now?" A medical report showed he had had 50 separate injuries.

In August 2004 he was arrested after the US requested his extradition, alleging he ran a support network for terrorists in Chechnya and Afghanistan.

Straw told the Commons yesterday that no minister was involved in the decision to bug Khan. He appointed Sir Christopher Rose, the chief surveillance commissioner and former appeal court judge, to inquire and report within two weeks if possible. Even if the facts of the surveillance operation are established, the government and police could argue that no rules or laws have been broken.

Straw told the Commons that any bugging of "phone calls and other public telecommunications" required a warrant signed by the home secretary or foreign secretary. But rules for other surveillance operations were different, requiring only authorisation from a chief police officer.

Gordon Brown's spokesman said last night that there may still be implications for the Wilson doctrine. "The government thinks it's important there is a full and thorough inquiry."